Doncaster Coroners' Court was told how Jeffrey Wragg, a retired steel worker, became a prisoner at HMP Doncaster in January of last year.
In a statement read out in court from Mr Wragg's cell mate, Jason Madden,the court was told how he and the 70-year-old were locked in their cell at around 6.15pm on November 30, and he fell asleep some time later.
When he awoke at around 11.40pm that evening, Mr Madden said he found Mr Wragg struggling to breathe and went to ask for assistance immediately.
The court was told that Mr Wragg had suffered a heart attack and his condition deteriorated quickly, the onset of which had begun between 24 hours and three days earlier.
A prison nurse was brought to the cell, and found Mr Wragg unconscious and was also not breathing. CPR was carried out on Mr Wragg, which managed to resuscitate him.
An ambulance arrived on the scene approximately 18 minutes after the alarm was raised, and he was transported to Doncaster Royal Infirmary but suffered another cardiac arrest on the way.
Mr Wragg was later transported to the specialist cardiac department at Northern General Hospital in Sheffield, but despite the best efforts of medics Mr Wragg died in hospital on December 1.
Coroner Louise Slater recorded Mr Wragg's cause of death as being a heart attack, with a cardiac atheroma - an accumulation of degenerative material in the inner layer of an artery wall - and smoking noted as contributing primary factors. Two of Mr Wragg's pre-existing conditions, emphysema and lung cancer, were recorded as secondary factors.
Dr Mark Pickering, a GP at the prison, said Mr Wragg was given a medical assessment shortly after arriving at the prison, and told medics he did not suffer from any chronic conditions or take any medication regularly.
Mr Wragg was noted as having high blood pressure, and a number of appointments with Dr Pickering were booked for Mr Wragg between February and April 2016, during which the dangers of high blood pressure were explained and it was suggested he take medication for them.
Dr Pickering told the court that Mr Wragg initially refused the medication because he was under the impression that he would need to come and collect it every day. After Dr Pickering explained that would not be necessary, Mr Wragg agreed to have medication to help with his high blood pressure prescribed but failed to collect it.
Mr Wragg called medical staff to his cell on two occasions in November saying he felt unwell. His blood pressure was taken on each occasion, and was found to be extremely high both times. Medical staff suggested Mr Wragg take medication to bring his blood pressure down but he refused.
Coroner Louise Slater recorded a conclusion of natural causes and passed her condolences on to Mr Wragg's family.